For a long time, changing your gender on government documents across Canada required proof of transitional surgery. More recently, this rule has been dropped to allow those in transition to choose for themselves when is the most appropriate time to officially change their gender.
The specific rules and requirements differ from province to province, but many have similar procedures. In Ontario, the procedures are somewhat different depending on your age when you apply. Those 15 years of age and under must apply as a child, while 16-17 year olds can choose to apply as a child or as an adult. Those over 18 years of age must apply as an adult.

Applying for a Change of Sex Designation as an Adult

Before you can begin the process, it is important to know that you can only request this change from the province or territory in which you were born, therefore to apply in Ontario your birth must be registered there. You will need to download and submit several forms and supporting documents in order to apply. These documents include:

An Application for Change of Sex Designation on Birth Registration of an Adult form, available here;

A Statutory Declaration for a Change of Sex Designation on a Birth Registration of an Adult form, available here;